My Emachine T3062 is Tweaking

Ok this one is more of a hardware question. If ryan or laurie can link this post to their blog I would definitely appreciate it. I was wondering if anyone can help me out with my current situations. I have an eMachines T3062 AMD Athlon XP 3000+ / 2GB DDR / 160GB HDD / DVD±RW Dual-Layer / Flash Media Reader / NVIDIA GeForce 4 MX / 10/100Mbps LAN / Windows XP Pro SP3 and I am having trouble with it. It seems that whenever I turn the computer on it begins to load on the windows xp screen and then the computer freezes, the screen going blank. I hear this low beep (one beep) which basically tells me my computer is frozen. I try turning it on and off a couple of times but and it does the same thing. Sometimes the screen will load and then it will freeze and turn off. My monitor (ViewSonic A95f) light will go from green to blinking like the computer is turned off. I took my computer to Comp USA and they told me nothing was wrong with it. They even showed me that it worked just fine but it did the same thing there just once unlike at home where it did it repeatedly. I don't know if its the power supply on my computer or the power running through our home but the computer was working great for a couple of years. I just dont understand why this is happening and I want to know what I can do to fix this.

Thanks to anyone that can help.

The Very Frustrated Lil Angel